Carrier Aggregation (“CA”) is a major topic in the development of the current Third Generation Partnership Project (“3GPP”) Long Term Evolution (“LTE”) standard. Radio bandwidth is a limited resource, because there is a limited spectrum that can be used for LTE communications. However, CA allows for the effective bandwidth to be expanded because the bandwidth can be subdivided into multiple component carriers. A user can concurrently use multiple carriers to transmit a channel, which increases the overall bandwidth that the channel is being transmitted on.
A significant problem with CA is how power allocation is handled between multiple carriers. A single user device (“UE”) only has a set amount of power that it can use to transmit due to limitations of the power amplifier on the UE, and that power must be allocated between the multiple carriers. For example, if multiple carriers are transmitting the physical random access channel (“PRACH”), or if carriers are transmitting the PRACH at substantially the same time as the physical uplink shared channel (“PUSCH”), the physical uplink control channel, (“PUCCH”), or the sounding reference signal (“SRS”), then the UE must divide the available power from the power amplifier between the different carriers and channels.
In certain instances, different channels may have different priorities. For example, the PRACH may have a lower priority than the PUSCH, PUCCH, SRS, because the information on the PRACH is less important than one of the other channels. Therefore, a lower amount of power may be allocated to the PRACH than one of the other uplink channels. However, a low power on the PRACH may cause the PRACH to be dropped multiple times, which may significantly negatively impact the time synchronization between the UE and an enhanced node base station (“eNB”).